Numerical simulation of the ITER BTCC prototype case enclosure welding

•A combined heat source model was suitable to simulate the deep penetration laser welding on thick plate.•The simulation result could coincide with the actual welding process.•The welding deformation was controlled in the range of ±2 mm. The 20mm thick 316LN austenitic stainless-steel plate was used as a case material to protect the inner side superconductive winding pack to resist the electromagnetic cyclic loads during the operation. The enclosure welding of the BTCC(short for bottom and top correction coils) case was consist of 18mm thick laser welding and 2mm TIG cover welding. To control the welding deformation of the large-scale prototype case, the numerical simulation was carried out to obtain the deformation distribution of the case. The result shows that the combined heat source model with double ellipsoid heat source and 3D Gauss heat source model was suitable to simulate 18mm thickness deep penetration laser welding and the warping deformation happened at both ends of the BTCC case. Although some simplification has been applied on the calculated model, the result could still consistent with the actual welding process. The established heat source and the result of the simulation process which will be benefit to predict the welding deformation of the BTCC case enclosure welding.